Season overview

Published 12 December 13

For many farmers 2013 has been a very difficult year to manage grass; rehousing in April after a late spring, and a significant drought in July was separated by periods of bumper grass growth.

As we now collate the last of the grass figures for 2013 from the Forage for Knowledge (FfK) grass measurement farms, DairyCo R&D manager Dr Debbie McConnell takes a look back at what has turned out to be a volatile season.

Grass growth

This year we have seen large volatility in growth rates throughout the season on the ten FfK farms. A very late spring with mean air temperatures, typically three degrees lower than the long term average in March, (Fig 2), meant daily growth rates in March (and April) failed to rise much above 12kg DM/ha. In contrast, grass growth in March and April of the three preceding years (2010-2012) averaged 33kg DM/ha/day (Fig 1).

Figure 2: Mean monthly UK temperatures for 2013 in comparision to the 1981-2010 average (Met Office, 2013). Until July, temperatures remained below the long term average.

Naturally this had a significant impact on spring grass yields, and by the end of April the total grass growth recorded was only one quarter (742kg DM/ha) of that recorded in previous years (2010-2012; 2663kg DM/ha) in the FfK programme.

May saw a jump in grass growth to rates in excess of 80kg DM/ha/day which accompanied a three degree rise in mean daily temperatures (9.5oC). This was the beginning of a period of good compensatory growth for the months of May and June; this went some way towards recouping the lost herbage from earlier in the season.

In total, May and June produced 16% more grass (625kg DM/ha) than the previous three years average and took total herbage production for the 2013 season up to 5282kg DM/ha (89% of the three year average).

Grass growth however, remained volatile for the remainder of the season with drought conditions taking hold in July. Growth rates fell on all ten FfK farms to an average of 31kg DM/day on 26 July.

Apart from a brief dip in growth rates in the first two weeks of September, due to drier conditions, grass growth for the months of August and September was 12% higher than the previous three year average.

In addition, mild dry conditions in October have provided excellent conditions for grass growth with 50% more grass grown than the 2010-2012 average. This has meant many farmers extending grazing this autumn with covers potentially high at the time of housing.

As a result of these conditions, somewhat surprisingly grass production over the season (up to 31 October) has been slightly above the 2010-2012 average (11905kg DM/ha vs. 11708kg DM/ha; Fig. 3) on the ten FfK farms however these results did vary between individual farms.

Unlike grass growth rates, grass quality has remained mainly constant over the season. Some fluctuations in DM content were evident at the start of the season and typically DM remained on average 2% higher than the 2010- 2012 average, a reflection of the lower rainfall volumes in 2013 (Fig 4). There was approximately 135mm less rainfall between the months of February and October this year, compared to the previous three years.

Figure 4: Measured grass DM content over the 2013, 2010-2012 seasons.

Likewise ME remained relatively constant over the season remaining slightly lower on average (0.3) than the previous three years. However, an average of 12.25 ME was achieved on the FfK farms over the season, a testament to the management of grass throughout the season on these farms (Fig 5).

Figure 5: Grass ME content over the 2013, 2010-2012 season on the FfK farms.

In contrast, Crude Protein (CP) levels in grass rose substantially in August, September and October (Fig 6). This is most likely a reflection of both the weather, with higher N mineralisation rates occurring as soil temperatures rose, and also as a response to surplus soil N from applied fertilisers, which was not utilised during the periods of low growth early in the season. Protein levels remained good into October, with CP levels in excess of 30% being measured on two farms in October.

The comments we got back from our FfK farmers, many of which were included in the newsletters, showed just how adaptable they had to be when dealing with the fluctuations in grass growth. From buying in forage in spring time to preserve the grass wedge, to topping to maintain residuals during high growth periods and grazing into late November and early December to make the most of the available grass and reduce housing costs, FfK farmers were flexible in order to make the most off, and preserve the future of, the quality feed grazed grass.